Inflammation on the bursa guiding the heel known as Retrocalcaneal Bursitis. Repetitive pressure or friction above the back again on the heel triggers the bursa to swell causing heel pain and tenderness, swelling and ankle stiffness. Normally connected to Achilles Tendonitis and Haglunds Deformity.   Ice. Instantly use an ice pack https://emilionblue.ampblogs.com/the-smart-trick-of-ankle-pain-singapore-that-no-one-is-discussing-70873643